FIELD OF INVENTION
[0001] The subject matter of the present application is related to spatial light modulators,
and in particular to subpixel layouts for a spatial light modulator that is used in
a directional display apparatus or system, such as a three-dimensional (3D) autostereoscopic
display apparatus, or a multi-view display.
BACKGROUND
[0002] A display apparatus that is capable of producing at least two different images simultaneously
is referred to herein as a directional display apparatus. A directional display produces
at least two different images, each of which is viewed from a different viewing position.
In one type of directional display device, the two images are intended to be viewed
as distinct separate images. Such a display may also be referred to as "a multi-viewer
display," multi-view display" or "multi-user display" which may be configured so that
different observers see different images. This allows for multiple simultaneous uses
of the display. A multi-view display may also be configured for use by a single observer.
[0003] A directional display may also be configured to produce at least two separate images
that are intended to be fused into a single image by the observer. Normal human vision
is stereoscopic such that each eye sees a slightly different image of the world. In
a three dimensional display apparatus, a separate image is provided to each eye, and
the brain of the observer fuses the stereo pair of images to give the appearance of
depth in the fused image.
[0004] A three dimensional display apparatus is typically classified as being either stereoscopic
or autostereoscopic. In a 3D stereoscopic display apparatus, some kind of viewing
aid is worn by the user to substantially separate the views sent to the left and right
eyes. For example, the viewing aid may be color filters in which the images are color
coded (e.g. red and green), polarizing glasses in which the images are encoded in
orthogonal polarization states, or shutter glasses in which the views are encoded
as a temporal sequence of images in synchronization with the opening of the shutters
of the glasses. In contrast, a 3D autostereoscopic display apparatus operates without
the need for the observer to wear a viewing aid. In autostereoscopic displays, each
of the views can be seen from a limited region in space.
[0005] WO 2006/107979 discloses a 2D display device having a display panel configured with a subpixel layout.
The display device comprises a pre-subpixel rendering detection component for detecting
an input image location of each of a plurality of pre-subpixel rendered image data
values. The display device further comprises a subpixel rendering component for performing
a subpixel rendering operation on the input image data to produce subpixel rendered
image data values ready for display on the subpixel layout of the display panel.
[0006] US 2003/128225 discloses various subpixel octal groupings for a color flat panel display.
[0007] GB 2403864 discloses an autostereoscopic display apparatus that comprises a spatial light modulator
comprising an array of pixel arranged in rows and columns in a pixel plane, and a
spatially multiplexing parallax element capable of directing light from successive
columns of pixels towards successive ones of two or more viewing windows in a nominal
window plane.
[0008] US 2006/244761 discloses a three-dimensional (3D) display and a method for subpixel rendering for
the 3D display.
Overview of Directional Display Devices
[0009] U.S. Patent 7,058,252, entitled "Optical Switching Apparatus" and issued to Woodgate et al., provides a
comprehensive discussion of the technical features and issues related to directional
displays, and in particular autostereoscopic 3D displays. In general, an autostereoscopic
system comprises a display panel and an optical steering element or mechanism for
directing the light from at least two separate images. The optical steering mechanism
may also be referred to as an optical director, parallax optic, or parallax barrier.
The optical steering mechanism sends the light from a left image to a limited region
in front of the display panel, referred to as a first viewing window. When the observer
places their left eye at the position of the first viewing window, then the observer
sees the appropriate image across the whole of the display panel. Similarly, the optical
steering mechanism sends the light intended for the right image to a separate second
viewing window. When the observer places their right eye in the second viewing window,
the right eye image will be seen across the whole of the display. Generally, the light
from either image may be considered to have been optically steered (i.e. directed)
into a respective directional distribution. The viewing window plane of the display
represents the distance from the display at which the lateral viewing freedom is greatest.
[0010] FIG. 1 herein illustrates an exemplary flat panel autostereoscopic display 10 as
shown in Figure 5 of
US 7,058,252. Display 10 comprises a backlight, an array of electronically adjustable pixels (known
as a spatial light modulator, SLM) arranged in columns and rows and a parallax barrier
attached to the front of the display which acts as the optical steering mechanism.
The term "spatial light modulator" includes both light valve devices such as liquid
crystal displays and emissive devices such as electroluminescent displays and LED
displays. A backlight 60 produces a light output 62 which is incident on an LCD input
polarizer 63. The light is transmitted through a TFT LCD substrate 66 and is incident
on a repeating array of pixels arranged in columns and rows in an LCD pixel plane
67. The red pixels 68,71,74, green pixels 69,72,75 and blue pixels 70,63 each comprise
an individually controllable liquid crystal layer and are separated by regions of
an opaque mask called a black mask 76. Each pixel comprises a transmissive region,
or pixel aperture 78. Light passing through the pixel is modulated in phase by the
liquid crystal material in the LCD pixel plane 67and in color by a color filter positioned
on an LCD color filter substrate 80.
[0011] The light then passes through an output polarizer 82 after which is placed a parallax
barrier 84 and a parallax barrier substrate 86. In FIG. 1, the parallax barrier 84
comprises an array of vertically extended transmissive regions separated by vertically
extended opaque regions and serves to direct light from alternate pixel columns 69,71,73,75
to the right eye as shown by the ray 88 for light from pixel 69 and from the intermediate
columns 68,70,72,74 to the left eye as shown by the ray 90 (this overall light direction
pattern forming another example of a directional distribution of light). The observer
sees the light from the underlying pixel illuminating the aperture of the barrier,
92. Other types of optical directors or parallax optics may be used in 3D displays,
such as a lenticular screen and birefringent lenses.
[0012] With continued reference to FIG. 1, the repeating array of pixels arranged in columns
and rows in LCD pixel plane 67 are separated by gaps, (generally defined by the black
mask in a liquid crystal display, LCD) with the parallax barrier being an array of
vertically extended slits of pitch close to twice the pitch of the pixel columns.
The parallax barrier limits the range of angles from which light from each pixel column
can be seen, thus creating the viewing windows at a region in front of the display.
[0013] In order to steer the light from each pixel to the viewing window, the pitch of the
parallax barrier is slightly smaller than twice the pitch of the pixel array. This
condition is known as "viewpoint correction". In the type of display illustrated in
FIG. 1, the resolution of each of the stereo pair images is half the horizontal resolution
of the base LCD, and two views are created. Thus, the light from the odd columns of
pixels 68,70,72,74 can be seen from the left viewing window, and the light from the
even
columns of pixels 69,71,73,75 can be seen from the right viewing window. If the left
eye image data is placed on the odd columns of the display and the right eye image
data on the even columns then the observer in the correct "orthoscopic" position should
fuse the two images to see an autostereoscopic 3D image across the whole of the display.
[0014] U.S. 7,154,653 entitled "Parallax Barrier and Multiple View Display" and issued to Kean et al.,
discloses various embodiments of parallax barriers for use in both multi-user and
3D displays. The background discussion of
US 7,154,653 and the figures referenced therein from columns 1 through column 5 discuss the characteristics
of parallax optics that may be varied or modified in order to control the size of,
and the angle between, viewing windows, or viewing regions, to which the multiple
images (e.g., left eye and right eye) produced by the display are directed. The function
of the parallax optics is to restrict the light transmitted through the pixels to
certain output angles, thereby defining the angle of view of the pixels behind a specific
part of the parallax optic structure (e.g., a slit or lenslet or lenticule.) For flat
panel autostereoscopic displays, the formation of the viewing regions is typically
due to a combination of the pixel structure of the display unit and the light-directing
optical element, or parallax optic.
[0015] U.S. 7,154,653 discloses the display 30 shown in FIG. 2A herein. Display 30 is a two view direction
display which may be used as an autostereoscopic 3D display or as a display for providing
two unrelated views to one or more observers. The display comprises a spatial light
modulator in the form of a liquid crystal display (LCD) 20. LCD 20 is pixellated,
which is defined herein to indicate a display that substantially comprises a subpixel
repeating group of at least two primary color subpixels. LCD 20 operates in transmissive
mode so as to modulate light passing through the subpixels from a backlight (not shown).
However,
U.S. 7,154,653 notes that other types of display may be used to modulate light in transmissive or
reflective modes or to generate light within the display device itself (in the case
of a front parallax barrier arrangement). Display 30 also comprises a parallax barrier
21 disposed in front of LCD 20, i.e. between the LCD 20 and the viewer or viewers.
Barrier 21, illustrated in more detail in FIG. 2B herein, provides regions 22 and
23 which are substantially opaque to light from the LCD 20 and slits therebetween
which are substantially transmissive to light from the LCD 20. The regions 22 and
23 have a finite width and all of the slits have the same maximum light transmission.
The columns of subpixels of LCD 20 are formed with a substantially uniform pitch p
in a direction perpendicular to the longitudinal axes of the
columns, the direction of which is generally horizontal during normal use of the display.
The slits of barrier 21 are arranged non-periodically, extend parallel to the longitudinal
axis of the subpixel columns, and are arranged in evenly spaced groups of slits with
the slits in each group being evenly spaced. FIG. 2A also shows details of an illustrated
embodiment of parallax barrier 21 with respect to the size and arrangement of the
slits.
[0016] With continued reference to FIG. 2A, display 30 is driven by display driver 25 such
that image data for the two views which are to be displayed are interlaced as vertical
stripes. The display driver 25 may be arranged to receive images for display and to
interlace the data so as to ensure that the individual pixel columns display the correct
vertical slices of the images. The display driver 25 may form part of the display
or may be embodied partly or wholly within other apparatus, such as a computer, microprocessor
or the like. The images may be captured "real" images or may be computer-generated.
The images may form a stereoscopic pair for autostereoscopic 3D use of the display
or may be stereoscopically unrelated images. The slits of barrier 21 are aligned with
or adjacent to the middle lines of the columns of pixels. Display driver 25 supplies
vertical image slices to a group of four columns of pixels nearest each group of slits.
The slits of the barrier 21 cooperate with the pixellation of the LCD 20 so as to
define or create five viewing regions. In each of the viewing regions, each group
of slits restricts visibility of the columns of pixels such that two adjacent pixel
columns only are visible to a viewer viewing the display from the viewing region.
[0017] With reference to FIG. 2C, display driver 25 supplies the pixel image data to the
LCD 20 such that first and second image slices are provided from one of the images
and third and fourth image slices are provided from the other of the images. Thus,
the first and second images forming the first and second views are visible in the
viewing regions D and B, respectively. When providing autostereoscopic viewing, provided
the left and right eyes of the observer are in the viewing regions B and D, respectively,
a stereoscopic pair of images can be viewed correctly to provide the 3D effect. Conversely,
a viewer whose eyes are in the viewing region D can see one of the images but not
the other whereas a viewer whose eyes are in the region B can see the other image
but not the first image. The viewing regions to either side of the regions B and D
which are actually used contain 50% of each image, reducing the contribution to crosstalk
from neighboring viewing regions. Display 30 makes use of 50% of the available light
and each image is displayed by 50% of the subpixels so that the horizontal resolution
is 50% of the LCD resolution.
[0018] U.S. Patent 7,058,252 referenced above also describes a type of display that is capable of operating in
both 3D and two-dimensional (2D) modes. This type of display is referred to therein
as a "2D 3D switchable display" and
U.S. Patent 7,058,252 discusses several examples of such displays, one of which is illustrated in FIGS.
3A and 3B herein. FIG. 3A shows a display comprising a backlight 60, producing light
output 62 which is incident on an LCD input polariser 64, an LCD TFT substrate 66,
an LCD pixel plane 67 comprising an array of pixels arranged in columns and rows followed
by an LCD counter substrate 80, an array of birefringent lenses 138, followed by an
isotropic lens microstructure 134 followed by a lens substrate 132. The previous items
can be grouped as a directional display device 236. Following the directional display
device 236, a polarization modifying device 146 is positioned. One illustrative configuration
of the operation of the display in the 2D mode is also shown along the propagation
direction 238. The polarization modifying device 146 transmits horizontal linearly
polarized light and extinguishes vertically polarized light. The LCD input polarization
240 is at 90-degrees and is rotated by the ON state of the liquid crystal material
in the pixel apertures 78 to a horizontal polarization (0-degrees angle) 242 by the
twisted nematic layer, thereby providing a normally white (NW) mode. In the NW mode
ON state, no voltage is applied to the liquid crystal layer. Voltage is applied to
switch the output to an OFF state, or intermediate levels. The birefringent microlenses
138 are index matched in this polarization and so do not impart any directionality
to the illumination. The output of the polarization modifying device 146 is horizontal
linear polarization 244.
[0019] FIG. 3B shows the configuration for the 3D operation of the display shown in FIG.
3A, along the propagation direction 238. In this case, the polarization modifying
device 146 is arranged to transmit vertically linearly polarized light and extinguish
horizontally polarized light. The LCD input polarization 240 is at 90-degrees and
is not rotated by the ON state of the liquid crystal material to a horizontal polarization
(0-degrees angle) 242 by the twisted nematic layer, thereby providing a normally black
(NB) mode. In the NB mode ON state, voltage is applied to the liquid crystal layer.
Reducing voltage is applied to switch the output to an OFF state, or intermediate
levels. The polarization state 246 incident on the birefringent microlenses 138 is
given directionality by the birefringent lens 138. In this case, the polarization
modifying device 146 is configured to transmit vertical linear polarization state
248, such that the 3D mode illumination structure is transmitted.
[0021] U.S. Patent 7,058,252 referenced above also describes a multi-user display embodiment, shown herein in
FIG. 4. FIG. 4 shows in plan view a birefringent microlens display 406 producing viewing
windows 408, 410, 412 and 414. The window size is arranged to be greater than the
interocular separation of the viewers. Display 406 is suitable for use, for example,
on the dashboard of an automobile. The driver places his right eye 416 in window 408,
and also his left eye 418 in the same window 408. Similarly the passenger places his
left eye 422 and right eye 420 in a single window 414. For a two view display, windows
408 and 412 contain the same information and windows 410 and 414 contain the same
information. For aberrational design purposes, it may be convenient to have the windows
410 and 412 between the passenger and driver of the display. If a first image 426
and a second image 428 are input, then an image signal interlacer 424 will put image
426 on the even columns of the display for example, and image 428 on the odd columns
of the display for example. The optical elements of the display will direct image
426 to the driver in window 408 and image 428 to the passenger in window 414.
U.S. Patent 7,058,252 notes that the display operates in the same manner as the 2D 3D switchable displays
described therein, except that viewing windows 408, 410, 412 and 414 are substantially
larger than the viewing windows produced by the 2D 3D switchable displays to allow
for different viewers to be positioned in different windows.
U.S. Patent 7,058,252 further notes that such multi-viewer displays may have two modes of operation: in
one mode of operation all viewers can see the same image and in a second mode of operation
different viewers can see different images to allow multiple simultaneous uses of
the same display.
[0022] U.S. Patent 6,424,323, entitled "Electronic Device Having a Display" and issued to Bell et al., also discloses
an electronic device having a display and an image deflection system overlying the
display, wherein the display is controlled to provide at least two independent display
images which, when displayed through the image deflection system, are individually
visible from different viewing positions relative to the display. One embodiment of
an image deflection system disclosed is a lenticular screen comprising a plurality
of lenticles (also referred to as lenticules.) The lenticles
extend across the display so that different images are visible as a function of the
angle of inclination of the viewer with respect to the screen. In this way, a single
user may view the different images by tilting the device about a horizontal axis.
Viewing Window Performance Issues
[0023] The term "cross talk" refers to light leakage between the two views such that some
of the left eye image will be seen by the right eye and vice versa. Cross talk generates
visual strain when viewing 3D displays, and control of cross talk is an important
factor in 3D display development. For flat panel autostereoscopic displays (in particular
those based on LCD technology), the limitation of window performance is generally
determined by the shape and aperture ratio of the pixel and the quality of the optical
element.
US Patent 7,058,252 referenced above notes that the angles of the output cone of light emitted from the
display are determined by the width and shape of the pixel aperture and the alignment
and aberrations of the parallax optic. The disclosure in
U.S. 7,154,653 further notes that attempts to reduce cross talk (i.e., light leakage between images)
by reducing the width of the slits in the parallax barrier may result in uneven color
balance as more of one color subpixel becomes visible to the observer, or the color
balance may change with the angle of view.
[0024] The disclosure in
U.S. 7,154,653 further notes that, in order to increase the lateral viewing freedom of the display,
more than two pixel columns can be placed under each slit of the parallax barrier.
For example, four columns will create four windows in which the view is changed for
each window. Such a display will give a "look-around" appearance as the observer moves.
The longitudinal freedom is also increased by such a method. However, in this case,
the resolution of the display is limited to one quarter of the resolution of the base
panel. Moreover, parallax barriers rely on blocking the light from regions of the
display and therefore reduce the brightness and device efficiency, generally to approximately
20-40% of the original display brightness.
[0025] U.S. 7,154,653 discloses that LCD 20 shown in FIG. 2A herein is of a "conventional" type of display
in which "white" pixels are divided into repeating groups of color sub-pixels. In
particular, the pixel columns of each group of three columns are provided with red,
green and blue filter strips so that all of color sub-pixels in each column display
the same color and adjacent pairs of columns display different colors with the pattern
red (R), green (G) and blue (B) repeating across the display.
U.S. 7,154,653 notes that, although the correct color balance is obtained for the right and left
views with such an arrangement, there is a substantial non-uniformity in the spacing
of single colors for each view. Such uneven spacing can be very visible in low resolution
displays, and therefore detracts from image quality. Also, for each view, the ordering
of the color sub-pixels does not follow the same repeating pattern of the three color
subpixels that comprise LCD 20; this is referred to as "crossing over" in the ordering
of the components of each white pixel, and such crossing over can lead to further
undesirable image artifacts.
U.S. 7,154,653 further discloses examples of alternative subpixel arrangements or layouts other
than the standard repeating RGB sub-pixel arrangement. One such arrangement provides
for no crossing over in the ordering of the sub-pixel components of a pixel that produces
a white color and reduces the spacing of individual color sub-pixels in each view,
with a goal of improving the image quality.
[0026] U.S. 6,023,315 entitled "Spatial light modulator and directional display" and issued to Harrold
et al., discloses a liquid crystal spatial light modulator comprising columns and
rows of picture elements, arranged as groups of columns, for instance under respective
parallax generating elements in an autostereoscopic 3D display. The picture elements
are arranged as sets to form color picture elements such that the picture elements
of each set are disposed at the apices of a polygon, such as a triangle, and are disposed
in corresponding columns of the groups of columns.
U.S. 6,023,315 comments on the deficiencies of using a spatial light modulator having the conventional
RGB vertical or horizontal stripe subpixel arrangement, or the known RGGB quad subpixel
arrangement, to produce stereoscopic images for a 3D display, citing problems with
color integration. In order to alleviate these problems,
U.S. 6,023,315 discloses various, embodiments of sub-pixel arrangements and groupings of sub-pixels,
called "tessellations," that are designed so that color integration occurs over a
substantially larger range of viewing distances. One set of several such arrangements
makes use of red, green, blue and white sub-pixels.
[0027] Against this background there is provided a directional display device according
to claim 1.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The accompanying drawings are incorporated in, and constitute a part of this specification,
and illustrate exemplary implementations and embodiments.
FIG. 1 is a diagrammatic plan view of a first exemplary flat panel autostereoscopic
display having parallax barrier structure
FIG. 2A is a diagrammatic view of a second exemplary flat panel autostereoscopic display
having a parallax barrier structure;
FIG. 2B is a plan view of a portion of the parallax barrier structure of the display
shown in FIG. 2A.
FIG. 2c is a diagrammatic view of the viewing windows produced by the display shown
in FIG. 2A.
FIG. 3A illustrates a diagram of a 2D 3D switchable display apparatus and the flow
of light therethrough when operating in a 2D mode.
FIG. 3B illustrates a diagram of a 2D 3D switchable display apparatus and the flow
of light therethrough when operating in a 3D mode.
FIG. 4 illustrates a diagram of a multi-viewer display apparatus that produces at
least two images in different viewing windows for viewing by at least two viewers.
FIG. 5 illustrates a two-dimensional spatial grid representative of input image signal
data;
FIG. 6 illustrates a matrix arrangement of a plurality of a subpixel repeating group
comprising subpixels in three primary colors that is suitable for a display panel.
FIG. 7 illustrates a resample area array for a primary color plane of the display
panel of FIG. 6, showing reconstruction points and resample areas.
FIG. 8 illustrates the resample area array of FIG. 7 superimposed on the two-dimensional
spatial grid of FIG. 5.
FIGS. 9A and 9B each illustrate a subpixel repeating group comprising subpixels in
three primary colors and white.
FIG. 10 illustrates the subpixel repeating group of FIG. 9A positioned on the two-dimensional
spatial grid of FIG. 5, and further showing a portion of a primary color resample
area array for the subpixel repeating group of FIG. 9A superimposed thereon.
FIG. 11 is a diagram illustrating a metamer filtering operation.
FIG. 12 is a flowchart for an embodiment of a metamer filtering operation followed
by a subpixel rendering operation.
FIG. 13 is a flowchart for an embodiment of a metamer filtering operation combined
with a subpixel rendering operation.
FIGS. 14A and 14B are block diagrams showing the functional components of two embodiments
of display devices that perform subpixel rendering operations.
FIG. 15 is a block diagram of a display device architecture and schematically illustrating
simplified driver circuitry for sending image signals to a display panel comprising
one of several embodiments of a subpixel repeating group.
FIG. 16A illustrates a portion of a display panel comprising a first embodiment of
a novel multi-primary color subpixel repeating group.
FIGS. 16B and 16C illustrates the subpixel arrangements of first and second image
views produced by the display panel of FIG. 16A when used in a directional display
device.
FIG. 17A illustrates a portion of a display panel comprising a second embodiment of
a novel multi-primary color subpixel repeating group.
FIGS. 17B and 17C illustrates the subpixel arrangements of first and second image
views produced by the display panel of FIG. 17A when used in a directional display
device.
FIG. 18A illustrates a portion of a display panel comprising a third embodiment of
a novel multi-primary color subpixel repeating group.
FIGS. 18B and 18C illustrates the subpixel arrangements of first and second image
views produced by the display panel of FIG. 18A when used in a directional display
device.
FIG. 19A illustrates a portion of a display panel comprising a fourth embodiment of
a novel multi-primary color subpixel repeating group.
FIGS. 19B and 19C illustrates the subpixel arrangements of first and second image
views produced by the display panel of FIG. 19A when used in a directional display
device.
FIG. 20A illustrates a portion of a display panel comprising a first embodiment of
a novel three primary color subpixel repeating group.
FIGS. 20B and 20C illustrates the subpixel arrangements of first and second image
views produced by the display panel of FIG. 20A when used in a directional display
device.
FIG. 21A illustrates a portion of a display panel comprising a second embodiment of
a novel three primary color subpixel repeating group.
FIGS. 21B and 21C illustrates the subpixel arrangements of first and second image
views produced by the display panel of FIG. 21A when used in a directional display
device.
FIG. 22A illustrates a portion of a display panel comprising a third embodiment of
a novel three primary color subpixel repeating group.
FIGS. 22B and 22C illustrates the subpixel arrangements of first and second image
views produced by the display panel of FIG. 22A when used in a directional display
device.
FIG. 23A illustrates a portion of a display panel comprising a fourth embodiment of
a novel three primary color subpixel repeating group.
FIGS. 23B and 23C illustrates the subpixel arrangements of first and second image
views produced by the display panel of FIG. 23A when used in a directional display
device.
FIG. 24A illustrates a portion of a display panel comprising a fifth embodiment of
a novel three primary color subpixel repeating group.
FIGS. 24B and 24C illustrates the subpixel arrangements of first and second image
views produced by the display panel of FIG. 24A when used in a directional display
device.
DETAILED DESCRIPTION
[0029] What follows is a discussion of display devices and systems that are configured with
display panels substantially comprising one of several embodiments of three primary
color or multi-primary color subpixel repeating groups that are particularly suitable
for directional display devices which produce at least two images simultaneously,
such as autostereoscopic three-dimensional display devices or multiview devices. Input
image data indicating an image is rendered to a device configured with one of the
illustrated subpixel repeating groups using a subpixel rendering operation.
[0030] Reference will now be made in detail to implementations and embodiments, examples
of which are illustrated in the accompanying drawings. Wherever possible, the same
reference numbers will be used throughout the drawings to refer to the same or like
parts.
[0031] The description that follows discusses several embodiments of subpixel arrangements
or layouts that are suitable for display panels in directional display devices of
the type described above. These subpixel arrangements depart from the conventional
RGB stripe layout, and some of these arrangements include more than three primary
colors. If input image data is specified in the conventional three-color "whole pixel"
RGB format, the input image data may be processed by a subpixel rendering (SPR) operation
in order to be rendered (displayed) on a display panel comprising one of these subpixel
arrangements. This description first presents an overview of subpixel rendering operations
and hardware configurations that are suitable for a display device having a display
panel comprising one of these subpixel arrangements, and then describes several exemplary
embodiments.
Overview of Subpixel Rendering Techniques
[0032] Commonly owned
U.S Patent No. 7,123,277 entitled "CONVERSION OF A SUB-PIXEL FORMAT DATA TO ANOTHER SUB-PIXEL DATA FORMAT,"
issued to Elliott et al., discloses a method of converting input image data specified
in a first format of primary colors for display on a display panel substantially comprising
a subpixel repeating group having a second format of primary colors that is different
from the first format of the input image data.
US 7,123,277 is hereby incorporated by reference herein for all that it teaches. The term "primary
color" refers to each of the colors that occur in the subpixel repeating group. When
a subpixel repeating group is repeated across a display panel to form a device with
the desired matrix resolution, the display panel is said to be substantially - comprised
of the subpixel repeating group. In this discussion, a display panel is described
as "substantially" comprising a subpixel repeating group because it is understood
that size and/or manufacturing factors or constraints of the display panel may result
in panels in which the subpixel repeating group is incomplete at one or more of the
panel edges. In addition, any display would "substantially" comprise a given subpixel
repeating group when that display had a subpixel repeating group that was within a
degree of symmetry, rotation and/or
reflection, or any other insubstantial change, of one of the illustrated embodiments
of a subpixel repeating group described in the appended claims. Reference to display
systems or devices using more than three primary subpixel colors to form color images
are referred to herein as "multi-primary" display systems. In a display panel having
a subpixel repeating group that includes a white (clear) subpixel, the white subpixel
represents a primary color referred to as white (W) or "clear", and so a display system
with a display panel having a subpixel repeating group including RGBW subpixels is
a multi-primary display system.
[0033] By way of example, an input image is presumed to be specified as a two-dimensional
array of color values specified in the conventional red (R). green (G) and blue (B)
triplet of data values, considered to be the first format of the input image data.
Each RGB triplet specifies a color at a pixel location in the input image. The display
panel substantially comprises a plurality of a subpixel repeating group that specifies
a second format in which the input image data is to be displayed. The subpixel repeating
group comprises subpixels in at least first, second and third primary colors that
are arranged in at least two rows on the display panel such that the subpixels of
two of the primary colors are arranged in what is referred to as a "checkerboard pattern."
That is, a second primary color subpixel follows a first primary color in a first
row of the subpixel repeating group, and a first primary color subpixel follows a
second primary color in a second row of the subpixel repeating group. Note that in
US 7,123,277, subpixels are also referred to as "emitters."
[0034] The operation of subpixel rendering the input image data produces a luminance value
for each subpixel on the display panel such that the input image specified in the
first format is displayed on the display panel comprising the second, different arrangement
of primary colored subpixels in a manner that is aesthetically pleasing to a viewer
of the image. As noted in
US 7,123,277, subpixel rendering operates by using the subpixels as independent pixels perceived
by the luminance channel. This allows the subpixels to serve as sampled image reconstruction
points as opposed to using the combined subpixels as part of a "true" (or whole) pixel.
By using subpixel rendering, the spatial reconstruction of the input image is increased,
and the display device is able to independently address, and provide a luminance value
for, each subpixel on the display panel.
[0035] In addition, another possible desirable feature of the subpixel rendering operation
might be to maintain color balance by ensuring that high spatial frequency information
in the luminance component of the image to be rendered does not alias with the color
subpixels to introduce color errors. An arrangement of the subpixels in a subpixel
repeating group might be suitable for subpixel rendering if subpixel rendering upon
such an arrangement may provide an increase in both spatial addressability, which
may lower phase error, and in the Modulation Transfer Function (MTF) high spatial
frequency resolution in both horizontal and vertical axes of the display. In the subpixel
rendering operation, the plurality of subpixels for each of the primary colors on
the display panel may be collectively defined to be a primary color plane (e.g., red,
green and blue color planes) and might be treated individually.
[0036] In one embodiment, the subpixel rendering operation may generally proceed as follows.
The color image data values of the input image data may be treated as a two-dimensional
spatial grid 50 that represents the input image signal data, as shown for example
in FIG. 5. Each square input sample area 52 of the grid represents the RGB triplet
of color values representing the color at that location of the image, with approximately
the same area filled physically by the RGB triplet. Each square input sample area
52 of the grid is further shown with a sample point 54 centered in input sample area
52.
[0037] FIG. 6 illustrates an example of a display panel taken from FIG. 6 of
US 7,123,277. The display panel comprising the plurality of the subpixel repeating group 10 is
assumed to have the same dimensions as the input image sample grid 50 of FIG. 5. In
FIG. 6 and in the other Figures that show examples of subpixel repeating groups herein,
subpixels shown with vertical hatching are red, subpixels shown with diagonal hatching
are green and subpixels 8 shown with horizontal hatching are blue. The location of
each primary color subpixel on display panel 5 approximates what is referred to as
a reconstruction point (or resample point) used by the subpixel rendering operation
to reconstruct the input image represented by spatial grid 50 of FIG. 5 on display
panel 5 of FIG. 6. Each reconstruction point is centered inside a resample area. The
plurality of resample areas for one of the primary colors comprises a resample area
array. FIG. 7 (taken from FIG. 9 of
US 7,123,277) illustrates an example of resample area array 7 for the blue color plane of display
panel 5, showing reconstruction (resample) points 17, roughly square shaped resample
areas 18 and resample areas 19 having the shape of a rectangle.
[0038] US 7,123,277 explains how the shape of resample area 18 may be determined in one embodiment as
follows. Each reconstruction point 17 is positioned at the center of its respective
subpixel (e.g., subpixel 8 of FIG. 6), and a grid of boundary lines is formed that
is equidistant from the centers of the reconstruction points; the area within each
boundary forms a resample area. A resample area then may be defined in one embodiment
by the area closest to its associated reconstruction point, and having boundaries
defined by the set of lines equidistant from other neighboring reconstruction points.
The grid that is formed creates a tiling pattern. Other embodiments of resample areas
are possible. For example, the shapes that can be utilized in the tiling pattern can
include, but are not limited to, squares, rectangles, triangles, hexagons, octagons,
diamonds, staggered squares, staggered rectangles, staggered triangles, staggered
diamonds, Penrose tiles, rhombuses, distorted rhombuses, and the like, and combinations
comprising at least one of the foregoing shapes.
[0039] Resample area array 7 is then overlaid on input image sample grid 50 of FIG. 5, as
shown in FIG. 8 (taken from FIG. 20 of
US 7,123,277.) Each resample area 18 or 19 overlays some portion of at least one input image sample
area 52 on input image grid 50 (FIG. 5). A set of fractions for each resample area
may then be formed. In one embodiment, the denominators of the fractions may be construed
as being a function of the resample area and the numerators as being the function
of an area of each of the input sample areas that at least partially overlaps the
resample area. The set of fractions collectively represent an image filter, also referred
to as a filter kernel, and may be stored as a matrix of coefficients. In one embodiment,
the total of the coefficients is substantially equal to one. The data values for each
input sample area is multiplied by its respective fraction and all products are added
together to obtain a luminance value for the resample area. In effect, the area ratios
of input to output are determined by either inspection or calculation and stored as
coefficients in filter kernels. The filter kernels are transform equations and are
generated by determining the relative area overlaps of both the original data set
sample areas and target display sample areas. The ratio of overlap determines the
coefficient values to be used in the filter kernel array. In the case of the square
shaped resample areas 18, each of these overlaps four input sample areas 52. Each
input sample area 52 thus contributes one-quarter (1/4 or 0.25) of its blue data value
to the final luminance value of resample point 17.
[0040] The subpixel rendering operation just described is an example of an image processing
technique referred to as area resampling. Other types of subpixel rendering techniques
may include resampling using bicubic filters, sinc filters, windowed-sinc filters
and any convolutions thereof.
[0041] In the example illustrated herein, the computations assume that the resample area
arrays for the three color planes are coincident with each other and with the input
image sample grid 50. It is also possible to align the resample area arrays differently,
relative to each other, or relative to the input image sample grid 50. The positioning
of the resample area arrays with respect to each other, or with respect to the input
image sample grid, is called the phase relationship of the resample area arrays.
[0042] Because the subpixel rendering operation renders information to the display panel
at the individual subpixel level, the term "logical pixel" is introduced. A logical
pixel may have an approximate Gaussian intensity distribution and overlaps other logical
pixels to create a full image. Each logical pixel is a collection of nearby subpixels
and has a target subpixel, which may be any one of the primary color subpixels, for
which an image filter will be used to produce a luminance value. Thus, each subpixel
on the display panel is actually used multiple times, once as a center, or target,
of a logical pixel, and additional times as the edge of another logical pixel. A display
panel substantially comprising a sub pixel layout of the type disclosed in
US 7,123,277 and using the subpixel rendering operation described therein and above achieves nearly
equivalent resolution and addressability to that of a convention RGB stripe display
but with half the total number of subpixels and half the number of column drivers.
Logical pixels are further described in commonly owned
U.S. Patent Application Publication No. 2005/0104908 entitled "COLOR DISPLAY PIXEL ARRANGEMENTS AND ADDRESSING MEANS" (
U.S. Patent Application No. 10/047,995). See also
Credelle st al., "MTF of High Resolution PenTile Matrix™ Displays," published in Eurodisplay
02 Digest, 2002, pp 1-4.
[0043] Examples of three-primary color and multi-primary color subpixel repeating groups,
including RGBW subpixel repeating groups, and associated subpixel rendering operations
are disclosed in the following commonly owned U.S. Patent Application Publications:
(1)
U.S. Patent Application Publication No. 2004/0051724 (
U.S. Application No. 10/243,094), entitled "FOUR COLOR ARRANGEMENTS AND EMITTERS FOR SUB-PIXEL RENDERING;" (2)
U.S. Patent Application Publication No. 2003/0128179 (
U.S. Application No. 10/278,352), entitled "COLOR FLAT PANEL DISPLAY SUB-PIXEL ARRANGEMENTS AND LAYOUTS FOR SUB-PIXEL
RENDERING WITH SPLIT BLUE SUB-PIXELS;" (3)
U.S. Patent Application Publication No. 2003/0128225 (
U.S. Application No. 10/278,353), entitled "COLOR FLAT PANEL DISPLAY SUB-PIXEL ARRANGEMENTS AND LAYOUTS FOR SUB-PIXEL
RENDERING WITH INCREASED MODULATION TRANSFER FUNCTION RESPONSE;" (4)
U.S. Patent Application Publication No. 2004/0080479 (
U.S. Application No. 10/347,001), entitled "SUB-PIXEL ARRANGEMENTS FOR STRIPED DISPLAYS AND METHODS AND SYSTEMS FOR
SUB-PIXEL RENDEREING SAME;" (5)
U.S. patent Application Publication No. 2005/0225575 (
U.S. Application No. 10/961,506), entitled "NOVEL SUBPIXEL LAYOUTS AND ARRANGEMENTS FOR HIGH BRIGHTNESS DISPLAYS;"
and (6)
U.S. Patent Application Publication No. 2005/0225563 (
U.S. Application No. 10/821,388), entitled "SUBPIXEL RENDERING FILTERS FOR HIGH BRIGHTNESS SUBPIXEL LAYOUTS."
[0044] U.S. 2005/0225575 entitled "NOVEL SUBPIXEL LAYOUTS AND ARRANGEMENTS FOR HIGH BRIGHTNESS DISPLAYS" discloses
a plurality of high brightness display panels and devices comprising subpixel repeating
groups having at least one white (W) subpixel and a plurality of primary color subpixels.
The primary color subpixels may comprise red, blue, green, cyan or magenta in these
various embodiments.
U.S. 2005/0225563 entitled "SUBPIXEL RENDERING FILTERS FOR HIGH BRIGHTNESS SUBPIXEL LAYOUTS" discloses
subpixel rendering techniques for rendering source (input) image data for display
on display panels substantially comprising a subpixel repeating group having a white
subpixel, including, for example, an RGBW subpixel repeating group. FIGS. 9 and 10
herein, which are reproduced from FIGS. 5A and 5B of
U.S. 2005/0225563, illustrate exemplary RGBW subpixel repeating groups 3 and 9 respectively, each of
which may be substantially repeated across a display panel to form a high brightness
display device. RGBW subpixel repeating group 9 is comprised of eight subpixels disposed
in two rows of four columns, and comprises two of red subpixels 2, green subpixels
4, blue subpixels 8 and white (or clear) subpixels 6. If subpixel repeating group
9 is considered to have four quadrants of two subpixels each, then the pair of red
and green subpixels are disposed in opposing quadrants, analogous to a "checkerboard"
pattern. Other primary colors are also contemplated, including cyan, emerald and magenta.
US 2005/0225563 notes that these color names are only "substantially" the colors described as "red",
"green", "blue",
"cyan", and "white". The exact color points may be adjusted to allow for a desired
white point on the display when all of the subpixels are at their brightest state.
[0045] US 2005/0225563 discloses that input image data may be processed as follows: (1) Convert conventional
RGB input image data (or data having one of the other common formats such as sRGB,
YCbCr, or the like) to color data values in a color gamut defined by R, G, B and W,
if needed. This conversion may also produce a separate Luminance (L) color plane or
color channel. (2) Perform a subpixel rendering operation on each individual color
plane. (3) Use the "L" (or "Luminance") plane to sharpen each color plane.
[0046] The subpixel rendering operation for rendering input image data in a conventional
RGB format onto a display panel comprising an RGBW subpixel repeating group of the
type shown in FIGS. 9A and 9B generally follows the principles disclosed and illustrated
in
US 7,123,277 and as described above, with some modifications. The subpixel rendering filter kernels
may be constructed using the area resampling principles described in
US 7,123,277. In one embodiment, a unity filter is used to map the incoming luminance data to
the white subpixels; that is, the luminance signal from one incoming conventional
image pixel directly maps to the luminance signal of one white subpixel in a subpixel
repeating group. The white subpixels reconstruct the bulk of the non-saturated luminance
signal of the input image data, and the surrounding primary color subpixels provide
the color signal information.
[0047] US 2005/0225563 discloses some general information regarding performing the subpixel rendering operation
for RGBW subpixel repeating groups that have red and green subpixels arranged in opposing
quadrants, or on a "checkerboard." The red and green color planes may use Difference
of Gaussian (DOG) Wavelet filter followed by an Area Resample filter. The Area Resample
filter removes any spatial frequencies that will cause chromatic aliasing. The DOG
wavelet filter is used to sharpen the image using the cross-color component. That
is to say, the red color plane is used to sharpen the green subpixel image and the
green color plane is used to sharpen the red subpixel image.
US 2005/0225563 discloses an exemplary embodiment of these filters as follows:
TABLE 1
-0.0625 |
0 |
-0.0625 |
|
0 |
0.125 |
0 |
|
-0.0625 |
0.125 |
-0.0625 |
0 |
0.25 |
0 |
+ |
0.125 |
0.5 |
0.125 |
= |
0.125 |
0.75 |
0.125 |
-0.0625 |
0 |
-0.0625 |
|
0 |
0.125 |
0 |
|
-0.0625 |
0.125 |
-0.0625 |
DOG Wavelet Filter |
+ |
Area Resample Filter |
|
Cross-Color Sharpening Kernel |
[0048] The blue color plane may be resampled using one of a plurality of filters, such as
2 x 2 box filter,
or a box-tent filter centered on the blue subpixel:
0.125 |
0.25 |
0.125 |
0.125 |
0.25 |
0.125 |
[0049] In one embodiment of producing the color signal information in the primary color
subpixels, each input pixel image data is mapped to two sub-pixels. In effecting this,
there are still a number of different ways to align the input image pixels with the
primary color subpixels in order to generate the area resampling filters. FIG. 10
(taken from FIG. 6 of
US 2005/0225563) illustrates an area resampling mapping of four input image pixels to subpixels in
the red color plane of a display panel having the subpixel repeating group shown in
FIG. 9A. Input image data is again depicted as shown in FIG. 5, as an array, or grid,
50 of squares, with each square 52 representing the color data values of an input
image pixel. Subpixel repeating group 3 of FIG. 9A, shown in the dark outline in FIG.
10, is superimposed upon grid 50 in an alignment in which two subpixels are substantially
aligned with the color image data of one input image pixel 52 on grid 50. Black dots
15 represent the centers of red subpixels 2 of subpixel repeating group 3. The resample
area array for the red color plane comprises red resample areas such as resample areas
14 and 16 that have a diamond shape, with the center of each resample area being aligned
with the center 15 of a red subpixel. It can be seen that the resample areas 14 and
16 each overlay a portion of several input image pixels. Computing the filter coefficients
for the area resample filter produces what is referred to as a "diamond" filter, an
example of which is the Area Resample Filter illustrated in Table 1 above.
[0050] FIG. 10 illustrates a specific alignment of the subpixel repeating group with the
input image pixel grid and the resample areas of the red color plane.
US 2005/0225563 discloses that any one or more aspects of the alignment of the input image pixel
grid with the subpixel repeating group, or with the resample areas for each color
plane, the choice of the location of the resample points vis-à-vis the input grid,
and the shapes of the resample areas, may be modified to simplify the area resample
filters that are produced. Several examples of such modifications are disclosed therein.
[0051] Commonly owned International Application
PCT/US06/19657 entitled MULTIPRIMARY COLOR SUBPIXEL RENDERING WITH METAMERIC FILTERING discloses
systems and methods of rendering input image data to multiprimary displays that utilize
metamers to adjust the output color data values of the subpixels. International Application
PCT/US06/19657 is published as
WO International Patent Publication No. 2006/127555. In a multiprimary display in which the subpixels have four or more non-coincident
color primaries, there are often multiple combinations of values for the primaries
that may give the same color value. That is to say, for a color with a given hue,
saturation, and brightness, there may be more than one set of intensity values of
the four or more primaries that may give the same color impression to a human viewer.
Each such possible intensity value set is called a "metamer" for that color. Thus,
a metamer on a display substantially comprising a particular multiprimary subpixel
repeating group is a combination (or a set) of at least two groups of colored subpixels
such that there exists signals that, when applied to each such group, yields a desired
color that is perceived by the Human Vision System. Using metamers provides a degree
of freedom for adjusting relative values of the colored primaries to achieve desired
goal, such as improving image rendering accuracy or perception. The metamer filtering
operation may be based upon input image content and may optimize subpixel data values
according to many possible desired effects, thus improving the overall results of
the subpixel rendering operation.
[0052] For example, in an RGBW system, a W subpixel is a metamer for the color grey with
a nearby group of R, G, and B subpixels. The subpixels that are used for creating
a given color may be any nearby subpixels that are close enough that the Human Vision
System will blend the colors together. These degrees of freedom -
choosing signal values from among similar color subpixels coupled with the degree
of freedom afforded by choosing among metamers, and thus signal values among different
sets of color subpixels -- allow the luminance component of a given image to be represented
possibly with greater fidelity at the subpixel level while maintaining the correct
brightness and color at a global (or perceptual) level. This freedom to select a color
from among various metamers thus creates a new possibility to improve images. For
example, a display can be designed to select metamers in such a way that the W subpixel
values are increased when they lie on the bright side of a high-frequency edge or
decreased when they lie on the dark side of high-frequency edges. When red and green
subpixel pairs fall on the bright side of a high-frequency edge in an image, it may
be desirable to select a metamer such that the R and G subpixel values are increased.
Conversely, when the red and green subpixel pair lies on the dark side of an edge,
the red and green subpixel values may be decreased.
[0053] WO 2006/127555 discloses at least two embodiments for implementing the functions of metamer filtering.
In one embodiment, a metamer filtering operation precedes a subpixel rendering operation
in the image processing pipeline, in effect combining the operations. In
WO 2006/127555, this is referred to as "direct metamer filtering." In a second embodiment, the metamer
filtering operation may be accomplished in a separate pass over the input image pixel
data. In
WO 2006/127555, this is referred to as "preconditioning metamer filtering."
[0054] WO 2006/127555 further discloses that, in terms of calculating metamers, it is possible to model
the dynamic relationships between metamer subpixel groups and associated signals.
For example, it is possible to find substantially linear relationships between the
metamers and signals of any particular color -- to allow calculating "nearby" metamers
and signals. Such a model could be used to adjust intensity values of subpixels comprising
a metamer in a manner so as to minimize image artifacts and errors - such as color
error or the like. From such a model, intensity adjustment values may be stored in
a display system and employed whenever there is a need to adjust image data in according
with certain data, such as luminance data. An example given for such adjustments is
described as follows: When one of the primaries in a metamer is changed by an amount
"a", one might change each of the other primaries by an amount "a*m" where the term
"m" is the 'metamer slope, which may be different for each of the primaries. The slope
term "m" may be calculated from the matrix M2X that converts colors from the multi-primary
system into CIE XYZ co-ordinates. It is known in the art to calculate this conversion
matrix from measurements of the chromaticity and luminosity of the primaries of a
multi-primary system, as discussed, for example, in co-owned United States Patent
Application Nos.
2005/0083341 and
2005/0083352.
WO 2006/127555 provides a methodology for computing the metamer slope term "m" for a given set of
primary colors on a particular display.
[0055] FIG. 11 herein is taken from FIG. 11 in
WO 2006/127555, and schematically shows one embodiment of a metamer filtering operation. Input image
data is represented by luminance data 1102 and color data 1104. These data sets may
be substantially coincident spatially - e.g. 1102 is the luminance data of image data
1104. Luminance channel 1102 is sampled for high frequency information with a filter
kernel 1110. This filter may be applied to a 3x3 area centered on a blue-white (BW)
pixel pair 1106. The result is a sharpening value 'a', which is used to change the
metamer of a color in box 1112. For each value 1106 in the luminance channel 1102,
there is a corresponding R G B and W value 1108 shown diagrammatically in the color
channels 1104. The RGBW values have their metamer changed in step 1112. The resulting
metamer 1116 is stored in output buffer 1114 or passed on to the next step of processing.
The red-green (RG) subpixel pairs are processed in a similar fashion (not shown in
figures here) but with a different filter kernel. Values centered on an RG subpixel
pair are sampled from the luminance channel and convolved with the filter kernel.
The resulting sharpness value 'a' is used to calculate a new metamer for an RGBW value
from the color channels. The resulting new metamer is stored in an output buffer or
passed on to the next step of processing. FIG. 12, taken from FIG. 15 in
WO 2006/127555, illustrates such an embodiment.
WO 2006/127555 discloses that the filter kernels shown and described therein are exemplary only,
and that other filter kernels may be employed to obtain different values that reflect
different relationships between the metamers (for example, a non-linear relationship,
or different input image data dimensions, or the like).
[0056] WO 2006/127555 further discusses the use of the metamer filtering operation in combination with
other subpixel rendering (SPR) techniques, such as the subpixel rendering operation
for high brightness layouts described above from
US 2005/0225563. Rather than performing the metameric filtering operation as a preconditioning step,
it is possible to construct the SPR operation so that it directly performs metamer
filtering with subpixel rendering in a single pass. Very generally, using area resampling
principles, a sharpening area filter kernel is computed for each color plane and subtracted
from an area resampling filter for that color plane to produce a metamer sharpening
wavelet filter. The reader is referred to
WO 2006/127555 for additional details. FIG. 13, taken from FIG. 17 in
WO 2006/127555, illustrates such an embodiment.
[0057] WO 2006/127555 also notes that, for all of the figures showing subpixel repeating groups presented
therein, additional subpixel layouts may be produced by replacing all or some of the
white subpixels with either cyan, yellow, grey or other colors. In addition, the techniques
discussed therein encompass the scope of all manners of display technologies, including
transmissive and non-transmissive display panels, such as Liquid Crystal Displays
(LCD), reflective Liquid Crystal Displays, emissive ElectroLuminecent Displays (EL),
Plasma Display Panels (PDP), Field Emitter Displays (FED), Electrophoretic displays,
Iridescent Displays (ID), Incandescent Display, solid state Light Emitting Diode (LED)
display, and Organic Light Emitting Diode (OLED) displays.
Overview of Display Device Structures for Performing Subpixel Rendering Techniques
[0058] FIGS. 14A and 14B illustrate the functional components of embodiments of display
devices and systems that implement the subpixel rendering operations described above
and in the commonly owned patent applications and issued patents variously referenced
herein. FIG. 14A illustrates display system 1400 with the data flow through display
system 1400 shown by the heavy lines with arrows. Display system 1400 comprises input
gamma operation 1402, gamut mapping (GMA) operation 1404, line buffers 1406, SPR operation
1408 and output gamma operation 1410.
[0059] Input circuitry provides RGB input data or other input data formats to system 1400.
The RGB input data may then be input to Input Gamma operation 1402. Output from operation
1402 then proceeds to Gamut Mapping operation 1404. Typically, Gamut Mapping operation
1404 accepts image data and performs any necessary or desired gamut mapping operation
upon the input data. For example, if the image processing system is inputting RGB
input data for rendering upon a RGBW display panel, then a mapping operation may be
desirable in order to use the white (W) primary of the display. This operation might
also be desirable in any general multiprimary display system where input data is going
from one color space to another color space with a different number of primaries in
the output color space. Additionally, a GMA might be used to handle situations where
input color data might be considered as "out of gamut" in the output display space.
In display systems that do not perform such a gamut mapping conversion, GMA operation
1404 is omitted. Additional information about gamut mapping operations suitable for
use in multiprimary displays may be found in commonly-owned U.S. patent applications
which have been published as
U.S. Patent Application Publication Nos. 2005/0083352,
2005/0083341,
2005/0083344 and
2005/0225562.
[0060] With continued reference to FIG. 14A, intermediate image data output from Gamut Mapping
operation 1404 is stored in line buffers 1406. Line buffers 1406 supply subpixel rendering
(SPR) operation 1408 with the image data needed for further processing at the time
the data is needed. For example, an SPR operation that implements the area resampling
principles disclosed and described above typically may employ a 3×3 matrix of image
data surrounding a given image data point being processed in order to perform area
resampling. Thus, three data lines are input into SPR 1408 to perform a subpixel rendering
operation that may involve neighborhood filtering steps. After SPR operation 1408,
image data may be subject to an output Gamma operation 1410 before being output from
the system to a display. Note that both input gamma operation 1402 and output gamma
operation 1410 may be optional. Additional information about this display system embodiment
may be found in, for example, commonly owned United States Patent Application Publication
No.
2005/0083352. The data flow through display system 1400 may be referred to as a "gamut pipeline"
or "gamma pipeline".
[0061] FIG. 14B shows a system level diagram 1420 of one embodiment of a display system
that employs the techniques discussed in
WO 2006/127555 referenced above for subpixel rendering input image data to multiprimary display
1422. Functional components that operate in a manner similar to those shown in FIG.
14A have the same reference numerals. Input image data may consist of 3 primary colors
such as RGB or YCbCr that may be converted to multi-primary in GMA module 1404. In
display system 1420, GMA component 1404 may also calculate the luminance channel,
L, of the input image data signal - in addition to the other multi-primary signals.
In display system 1420, the metamer calculations may be implemented as a filtering
operation which involves referencing a plurality of surrounding image data (e.g. pixel
or subpixel) values. These surrounding values are typically organized by line buffers
1406, although other embodiments are possible, such as multiple frame buffers. Display
system 1420 comprises a metamer filtering module 1412 which performs operations as
briefly
described above, and as described in more detail in
WO 2006/127555. In one embodiment of display system 1420, it is possible for metamer filtering operation
1412 to combine its operation with sub-pixel rendering (SPR) module 1408 and to share
line buffers 1406. As noted above, this embodiment is called "direct metamer filtering".
[0062] FIG. 15 provides an alternate view of a functional block diagram of a display system
architecture suitable for implementing the techniques and subpixel repeating groups
disclosed herein above and discussed below with respect to directional displays. Display
system 1550 accepts an input signal indicating input image data. The signal is input
to SPR operation 1408 where the input image data may be subpixel rendered for display.
While SPR operation 1408 has been referenced by the same reference numeral as used
in the display systems illustrated in FIGS. 14A and 14B, it is understood that SPR
operation 1408 may include any modifications to SPR functions that are discussed below
for the purpose of implementing subpixel rendering techniques on a display panel comprising
any one of the subpixel repeating groups also discussed below that are particularly
suitable for directional displays.
[0063] With continued reference to FIG. 15, in this display system architecture, the output
of SPR operation 1408 may be input into a timing controller 1560. Display system architectures
that include the functional components arranged in a manner other than that shown
in FIG. 15 are also suitable for the directional display systems contemplated herein.
For example, in other embodiments, SPR operation 1408 may be incorporated into timing
controller 1560, or may be built into display panel 1570 (particularly using LTPS
or other like processing technologies), or may reside elsewhere in display system
1550, for example, within a graphics controller. The particular location of the functional
blocks in the view of display system 1550 of FIG. 15 is not intended to be limiting
in any way.
[0064] In display system 1550, the data and control signals are output from timing controller
1560 to driver circuitry for sending image signals to the subpixels on display panel
1570. In particular, FIG. 15 shows column drivers 1566, also referred to in the art
as data drivers, and row drivers 1568, also referred to in the art as gate drivers,
for receiving image signal data to be sent to the appropriate subpixels on display
panel 1570. Display panel 1570 substantially comprises a subpixel repeating grouping
1720 of FIG. 17A, which is comprised of a two row by eight column subpixel repeating
group having four primary colors including white (clear) subpixels. It should be appreciated
that the subpixels in repeating group 1720 are not drawn to scale with respect to
display panel 1570; but are drawn larger for ease of viewing. As shown in the expanded
view, display panel 1570 may substantially comprise other subpixel repeating groups
as shown, particularly those shown in the figures and described in more detail below
that are particularly suitable for directional displays. One possible dimensioning
for display panel 1570 is 1920 subpixels in a horizontal line (640 red, 640 green
and 640 blue subpixels) and 960 rows of subpixels. Such a display would have the requisite
number of subpixels to display VGA, 1280x720, and 1280x960 input signals thereon.
It is understood, however, that display panel 1570 is representative of any size display
panel.
[0066] The techniques and subpixel repeating groups discussed herein above and in the discussion
that follows encompass the scope of all manners of display technologies, including
transmissive and non-transmissive display panels, such as Liquid Crystal Displays
(LCD), reflective Liquid Crystal Displays, emissive ElectroLuminecent Displays (EL),
Plasma Display Panels (PDP), Field Emitter Displays (FED), Electrophoretic displays,
Iridescent Displays (ID), Incandescent Display, solid state Light Emitting Diode (LED)
display, and Organic Light Emitting Diode (OLED) displays.
Subpixel Layouts and Subpixel Rendering for Directional Display Devices.
[0067] This description now turns to a discussion of exemplary embodiments of subpixel repeating
groups that are particularly suited for display panels used in directional display
devices that are capable of simultaneously displaying at least two images. As noted
in the Background discussion, a directional display device may be configured to display
at least two images that are intended to be viewed by a single observer from an optimal
viewpoint in order to create the perception of a single three-dimensional image. A
directional display device may also be configured to display at least two images each
of which is intended to be viewed by a single observer from first and second viewpoints,
or by two observers from first and second viewpoints. In many of the Figures showing
exemplary embodiments of subpixel repeating groups herein, the columns of subpixels
in the portion of the display panel illustrated are labeled as "L" and "R," indicating
that some of the columns of the display panel are directed to a "left view" (for example,
an observer's left eye in a 3D display system,) while other columns are directed to
a "right view." The "L" and "R" labeling is not intended to restrict the use of the
display panel in any way to an autostereoscopic device. What is intended is that when
a display panel substantially comprising a subpixel repeating group as shown in a
particular figure is used in a directional display device, the light emissions of
a first half of the columns (the "R" columns) are directed to produce a first image
visible from a first viewing point and the light emissions of the second half of the
columns (the "L" columns) are directed to produce a second image visible from a second
viewing point. These first and second images are referred to as views and the subpixel
arrangement that form the basis of each view is shown in a separate figure. It is
to be understood that the subpixel arrangement shown in a view is a subset of the
subpixels that form the originating display panel.
[0068] In some of the illustrated embodiments discussed below, the columns of subpixels
in the portion of the display panel illustrated are labeled as "L" "R," and "B." The
columns designated "B" are intended to be directed to both left and right views by
the optical steering mechanism or component of the display. These particular embodiments
are well-suited to autostereoscopic 3D displays in which the right and left eye views
share the chromatic information in the image. These particular embodiments may be
less suitable for mulit-view directional displays where the first and second images
do not share the same chromatic information.
[0069] In each of the illustrated embodiments described below, a display device having a
display panel substantially comprising the subpixel repeating group of the embodiment
is not restricted to use solely in a directional display device, and may operate in
a conventional single image or 2D mode, or in what is referred to above as a 2D 3D
switchable display. The subpixel rendering (SPR) operation (for example, SPR operation
1408 of display device 1400 of FIG. 14A or display device 1420 of FIG. 14B) may be
configured to receive input image data and produce output image data for each subpixel
on the display panel when operating in a 2D mode, using the area resampling and metamer
filtering techniques described in the discussion above and in the published patent
and patent application documents referenced herein. It is understood that a person
of skill in the art would be able to apply the principles taught in the aforementioned
documents to the subpixel repeating groups illustrated herein to produce the appropriate
filters to carry out the subpixel rendering operation, and those details are omitted
from the discussion that follows.
[0070] In the discussion of the exemplary embodiments of subpixel repeating groups that
follows, reference is made, and examples are shown, of subpixels arranged in a particular
color order and position in rows and columns. It is to be understood that in some
or all of the arrangements illustrated, the row positions of the subpixels may be
interchanged, such as when the subpixels in the first and second rows are interchanged.
In addition, in some or all of the arrangements illustrated, it is also to be understood
that reference to a particular order of the color subpixels in first and second rows
of a subpixel repeating group also encompasses arrangements in which the subpixel
repeating group is rotated 90 degrees to the right or left.
1. Mulitprimary Subpixel Repeating Group Embodiments
[0071] As a preliminary matter, each of the mulitprimary subpixel repeating group embodiments
illustrated in FIGS. 16A, 17A, 18A and 19A includes a white (W) subpixel as a primary
color. In each of these embodiments it is understood that the white subpixels may
be replaced by any other suitable color that functions as a primary color, such as
yellow, magenta, grey-blue, or cyan. The white subpixels may also be replaced by additional
instances of red, green, or blue subpixels. In addition, as noted in commonly owned
US 2005/0225563 which discusses additional embodiments of these high brightness layouts, these color
names are only "substantially" the colors described as "red", "green", "blue", "cyan",
and "white". The exact color points may be adjusted to allow for a desired white point
on the display when all of the subpixels are at their brightest state.
[0072] FIG. 16A shows a portion of a display panel substantially comprising subpixel repeating
group 1610. Subpixel repeating group 1610 comprises twelve (12) subpixels disposed
in two rows and comprising four red subpixels 1612, four green subpixels 1614, two
blue subpixels 1616 and two white (or clear) subpixels 1618. The blue subpixels 1616
and the white subpixels 1618 are disposed in the same columns forming stripes of alternating
blue and white subpixels. If the subpixel repeating group is viewed as having four
quadrants of three subpixels each, then the white subpixels 1618 and the blue subpixels
1616 are disposed in different rows in opposing quadrants, forming a low resolution
checkerboard pattern. A red subpixel 1612 is paired with a green subpixel 1614 in
each quadrant. In the first row, the green subpixel 1614 follows the red subpixel
1612 when moving across the row in the left to right direction, and in the second
row the red subpixel 1612 follows the green subpixel 1614. Such an arrangement of
the red and green subpixels could be viewed as a higher resolution checkerboard pattern.
[0073] A display device having a display panel substantially comprising subpixel repeating
group 1610 as shown in FIG. 16A may also operate as a directional display device.
FIG. 16B shows the view 1604 produced by columns 1624 of subpixels labeled "R" in
FIG. 16A. The image displayed in view 1604 is rendered on a subpixel repeating group
1630 comprising six subpixels disposed in two rows, and including two red subpixels
1612, two green subpixels 1614, one blue subpixel 1616 and one white subpixel 1618.
FIG. 16C shows the view 1602 produced by columns 1622 of subpixels labeled "L" in
FIG. 16A. The image displayed in view 1602 is rendered on a subpixel repeating group
1640 also comprising six subpixels disposed in two rows, and including two red subpixels
1612, two green subpixels 1614, one blue subpixel 1616 and one white subpixel 1618.
These particular subpixel repeating groups 1630 and 1640 are previously disclosed
and discussed in commonly owned
U.S. Patent Application Publication No. 2004/0051724, entitled "FOUR COLOR ARRANGEMENTS AND EMITTERS FOR SUB-PIXEL RENDERING," and
WO International Patent Publication No. 2006/127555, entitled "MULTIPRIMARY COLOR SUBPIXEL RENDERING WITH METAMERIC FILTERING." Thus,
the distinct "L" and "R" images produced on a display panel comprising subpixel repeating
group 1610 of FIG. 16A have all of the advantages discussed therein with respect to
images produced on display panels substantially comprising subpixel arrangements 1630
and 1640.
[0074] FIG. 17A shows a portion of a display panel 1700 substantially comprising subpixel
repeating group 1720. Subpixel repeating group 1720 comprises twenty four (24) subpixels
disposed in two rows and comprising eight green subpixels 1744, eight white (or clear)
subpixels 1748, four blue subpixels 1746 and four red subpixels 1742. The red subpixels
1742 and the blue subpixels 1746 are disposed in the same columns forming four columns
of alternating red and blue subpixels. The columns of red and blue subpixels are disposed
between pairs of green subpixels 1744 and white subpixels 1748 that form columns of
alternating green and white subpixels. Each row contains two red subpixels 1742 and
two blue subpixels 1746 that alternate in order from left to right, with blue subpixels
1746 following red subpixels 1742 in the first row, and red subpixels 1742 following
blue subpixels 1746 in the second row, forming a low resolution checkerboard pattern
of the red and blue primary colors. Paired green and white subpixels also alternate
in order from left to right in each row, forming a horizontally higher resolution
checkerboard pattern. The repeating pattern of the green (G) and white (W) subpixels
may be more easily seen in the example below using letters to represent the subpixel
color and location, where "x" is a placeholder for the blue and red subpixels in subpixel
repeating group 1720:
G |
W |
x |
W |
G |
x |
G |
W |
x |
W |
G |
x |
W |
G |
x |
G |
W |
x |
W |
G |
x |
G |
W |
x |
[0075] FIG. 17A has columns of subpixels 1724, 1722, and 1723 labeled "R," "L" and "B" respectively.
Columns 1723 labeled "B" comprising the red and blue alternating subpixels are directed
to both first (R) and second (L) images when a display device having a display panel
substantially comprising subpixel repeating group 1720 is operated as a directional
display device. In this embodiment, the color primaries are divided into two classes
of primaries based on their relative luminance, and the relatively darker primaries,
in this embodiment the red and blue primary color subpixels, are shared between the
left and right views. The Human Vision System can tolerate this because the chromatic
channels are not referenced when creating the mental impression of visual depth or
distance perception because the resolution of the chromatic channels is too low to
support the fine distinction between the two parallax separated views. Only the luminance
channel has the required resolution. Thus, the subpixels of the brighter primary color(s)
carry the burden of conveying the needed stereoscopic information. In addition, the
left and right views can share the chromatic information of these columns without
creating visual artifacts. The embodiment shown in FIG. 17A, then, is particularly
well-suited to autostereoscopic 3D displays and to switchable 2D 3D displays.
[0076] FIG. 17B shows the view 1734 produced by columns 1724 of subpixels labeled "R" and
columns 1723 of subpixels labeled "B" in FIG. 17A. The image displayed in view 1734
is rendered on a subpixel repeating group 1730 comprising eight subpixels disposed
in two rows, and including two subpixels each of red, green, blue and white. FIG.
17C shows the view 1732 produced by columns 1722 of subpixels labeled "L" and columns
1723 of subpixels labeled "B" in FIG. 17A. The image displayed in view 1732 is rendered
on a subpixel repeating group 1740 also comprising eight subpixels disposed in two
rows, and including two subpixels each of red, green, blue and white. The subpixel
repeating groups 1730 and 1740 of the first and second views are previously disclosed
and discussed in commonly-owned
U.S. Patent Application Publication No. 2005/0225575 entitled "NOVEL SUBPIXEL LAYOUTS AND ARRANGEMENTS FOR HIGH BRIGHTNESS DISPLAYS,"
and also in
WO 2006/127555 referenced above. Thus, the distinct "L" and "R" images produced on a display panel
comprising subpixel repeating group 1720 of FIG. 17A have all of the advantages discussed
therein with respect to images produced on display panels substantially comprising
subpixel arrangements 1730 and 1740.
[0077] The subpixel rendering operation used to render the first and second (e.g., left
and right) views may be modified to account for the fact that a subset of the subpixels
on display panel 1700 (i.e., columns 1723) are shared by the two views. The subpixel
rendering operation may average the contributions for the input image data belonging
to the two separate views 1734 and 1732 for those color planes corresponding to the
color subpixels in the columns 1723 shared by both views. In the embodiment shown
in FIG. 17A, the subpixel rendering operation may average the contributions for the
input image data belonging to the two separate views 1734 and 1732 for the red and
blue color planes. Additionally, it may be desirable to adjust the metamers selected
for each of the two views 1734 and 1732 such that the subpixels in the columns in
both views are most nearly the same. If one must be chosen over the other, it may
be desirable to select the metamers that most nearly bring the red-green chromatic
channel in each view most nearly together, since the Human Vision System is more sensitive
to error in this chromatic channel than to error in the yellow-blue chromatic channel.
In the case of the arrangement of subpixels 1720 of Fig. 17A, the red color plane
of each view is to be set most nearly identical.
[0078] FIG. 18A shows a portion of a display panel substantially comprising subpixel repeating
group 1810. Subpixel repeating group 1810 comprises twenty four (24) subpixels disposed
in two rows and comprising 16 white (or clear) subpixels 1818, 2 green subpixels 1814,
2 blue subpixels 1816, 2 red subpixels 1812 and 2 subpixels 1817 of a suitable fifth
color primary such as cyan, emerald, yellow, magenta, or other suitable color 1817.
In FIGS. 18A, 18B and 18C, fifth color primary subpixels 1817 represent the color
cyan, indicated by closely spaced horizontal hatching. The white subpixels 1818 are
disposed in two adjacent columns. Red subpixels 1812 alternate with cyan subpixels
1817 in two columns, and green subpixels 1814 alternate with blue subpixels 1816 in
two columns.
[0079] FIG. 18A shows columns 1824 and 1822 of white subpixels 1818, labeled "R" and "L"
respectively. Columns 1824 labeled "R" of the display panel are directed to the first
(R) image and columns 1822 of the display panel are directed to the second (L) image
when a display device having a display panel substantially comprising subpixel repeating
group 1810 is operated as a directional display device. Columns 1825 labeled "B" and
comprising the red and cyan alternating subpixels and columns 1823 comprising the
green and blue alternating subpixels are directed to both first (R) and second (L)
images when a display device having a display panel substantially comprising subpixel
repeating group 1810 is operated as a directional display device.
[0080] FIG. 18B shows the view 1804 produced by columns 1824 of subpixels labeled "R" and
columns 1823 and 1825 of subpixels labeled "B" in FIG. 18A. FIG. 18C shows the view
1802 produced by columns 1822 of subpixels labeled "L" and columns 1823 and 1825 of
subpixels labeled "B" in FIG. 18A. The embodiment shown in FIG. 18A is particularly
well-suited to autostereoscopic 3D displays and to switchable 2D 3D displays. As discussed
above with respect to the embodiment illustrated in FIGS. 17A, 17B and 17C, since
it is the luminance channel that has the required resolution needed by the Human Vision
System to produce the mental impression of visual depth or distance perception, it
is primarily the white subpixels in the embodiment of FIG. 18A that carry the burden
of conveying the needed stereoscopic information, while the saturated primary color
subpixels carry the chromatic information of the image without creating visual artifacts.
[0081] The image displayed in each of views 1804 and 1806 is rendered on a subpixel repeating
group 1830 comprising sixteen subpixels disposed in two rows, and including eight
white subpixels 1818, and two subpixels each of red, green, blue and cyan. It can
be seen that the white subpixels are disposed in a square arrangement across view
1804. That is, imaginary lines connecting the centers of four neighboring white subpixels
form a square. When subpixel repeating group 1830 is viewed as having four quadrants
of four pixels each, it can be seen that the pairs of saturated color primaries are
disposed in opposing quadrants, forming a checkerboard pattern. Subpixel repeating
groups having columns of white subpixels of the type illustrated in FIGS. 18B and
18C are previously disclosed and discussed in commonly-owned
US Patent Application Publication No. 2005/0225575, and in commonly-owned
WO 2006/127555, both referenced above. Thus, the distinct "L" and "R" images produced on a display
panel comprising subpixel repeating group 1810 of FIG. 18A have all of the advantages
discussed therein with respect to images produced on display panels substantially
comprising subpixel arrangement 1830.
[0082] FIG. 19A shows a portion of a display panel 1900 substantially comprising subpixel
repeating group 1910. Subpixel repeating group 1910 comprises eight (8) substantially
square shaped subpixels disposed in four rows and two columns and comprising two subpixels
of each primary color. The red subpixels 1912 and the blue subpixels 1916 are disposed
in the same rows forming two rows of alternating red and blue subpixels that are disposed
between rows of alternating green subpixels 1914 and white subpixels 1918. Each column
in subpixel repeating group 1910 contains one subpixel of each primary color. When
a display device having a display panel comprising subpixel repeating group 1910 operates
in the conventional 2D mode, four subpixels (one each of red, green, blue and white)
may be used to display information in a "whole pixel" mode, and the subpixel rendering
operation may be bypassed. When a display device having a display panel comprising
subpixel repeating group 1910 operates as a directional display device, such as in
3D mode, first and second image data may be split column by column, with image data
in columns 1924 labeled (R) going to produce view 1902 as shown in FIG. 19B, and image
data in columns 1922 labeled (L) going to produce view 1904 as shown in FIG. 19C.
[0083] View 1902 in FIG. 19B and view 1904 in FIG. 19C have some similarities. Each row
of data comprises 2 subpixel rows. Luminance centers will be either on a red-green
(RG) subpixel pair 1936 or blue-white (BW) subpixel pair 1938 (FIG. 19B). Each column
of image data can create full resolution in this mode of operation (e.g., in 3D) using
a subpixel rendering operation as described above with appropriate sharpening algorithms.
However, the color information must be spread to two or three pairs of rows in order
to achieve the correct color, which limits the resolution in the vertical axis. FIG.
19C shows the subpixels needed to achieve proper color. When the input image data
pixel whose color is to be produced is centered on red-green subpixel pair 1926, four
pairs of blue and white subpixels 1928, 1930, 1932, 1934 are used to balance the color.
Sharpening algorithms may be used to enhance the sharpness of horizontal lines in
the output image. Note that in display panels comprising subpixel repeating group
1910, in each of views 1902 and 1904 diagonal lines in the output image can have the
same modulation transfer function (MTF) they would have when the display panel operates
in the conventional 2D mode because in each of views 1902 and 1904 the subpixel colors
alternate in the columns.
2. Subpixel Repeating Group Embodiments with Three Color Primaries
[0084] FIG. 20A shows a portion of a display panel 2000 substantially comprising subpixel
repeating group 2010. Subpixel repeating group 2010 comprises six (6) subpixels in
three primary colors disposed in two rows. The blue subpixels 2016 are disposed in
columns forming vertical stripes. Each row contains one red subpixel 2012 and one
green subpixel 2014, with green subpixel 2014 following red subpixel 2012 in the first
row and the red subpixel 2012 following green subpixel 2014 in the second row, forming
a checkerboard pattern. Any three consecutive different primary color subpixels in
a row may be grouped together as a conventional whole pixel 2020. Thus, the display
panel may be treated as an array of full color conventional whole pixels 2020 when
operating in the 2D mode.
[0085] FIG. 20A has columns of subpixels 2024 and 2022 labeled "R" and "L" respectively.
Columns 2024 labeled "R" are directed to a first (R) image and columns 2022 labeled
"L" are directed to a second (L) image when a display device having a display panel
substantially comprising subpixel repeating group 2010 is operated as a directional
display device. FIG. 20B shows the view 2004 produced by columns 2024 of subpixels
labeled "R" in FIG. 20A. The image displayed in view 2004 is rendered on a subpixel
repeating group 2030 comprising six subpixels disposed in two rows, and including
two subpixels each of red, green and blue. Note that the subpixels substantially occupy
the same positions relative to subpixel repeating group 2010, including the vertical
stripe of blue subpixels. FIG. 20C shows the view 2002 produced by columns 2022 of
subpixels labeled "L" in FIG. 20A. The image displayed in view 2002 is also rendered
on subpixel repeating group 2030.
[0086] Variations of subpixel repeating group 2030 having a vertical blue stripe are previously
disclosed and discussed in commonly-owned
US Patents 7,123,277 and
6,903,754. Thus, the distinct "L" and "R" images produced on a display panel comprising subpixel
repeating group 2020 of FIG. 20A have all of the advantages discussed therein with
respect to images produced on a display panel substantially comprising the subpixel
arrangement of 2030. In particular, if display panel 2000 of FIG. 20A is used in a
conventional 2D mode to display images rendered in whole pixel mode (i.e, using whole
pixels 2020 and not using a subpixel rendering technique), it will have a given resolution,
r. The first (R) and second (L) images produced by this same panel when operating
as a directional display device will each have the same resolution r when a subpixel
rendering operation is used to render the image data for each view.
[0087] Alternatively, red subpixels 2012, green subpixels 2014 and blue subpixels 2016 of
display panel 2000 of FIG. 20A may be configured to have a narrow aspect ratio. This
would allow display panel 2000 when used in a conventional 2D mode of operation to
increase the resolution of the panel in the horizontal direction, and thereby improve
the image quality, by taking advantage of subpixel rendering for displaying images
in the 2D mode.
[0088] FIGS. 21A, 22A, 23A and 24A discuss embodiments in which the subpixel repeating group
of the display panel includes subpixels in one of the primary colors at a higher resolution
than subpixels of the other two primary colors. The subpixels that occur at the higher
resolution are referred to as the majority subpixels in the subpixel repeating group.
These particular embodiments use green subpixels as the majority subpixels, but it
is to be understood that there may be occasions (for example, a particular display
application) in which it may be suitable for the majority subpixels to be a different
primary color. In each of these embodiments, the majority subpixels are disposed in
the subpixel repeating group so as to form vertical or horizontal stripes on the display
panel. The minority subpixels are disposed in the subpixel repeating group in opposing
quadrants, in a manner similar to a checkerboard pattern. That is, if the subpixel
repeating group has N subpixels disposed in two rows of N/2 subpixels, then the subpixel
repeating group can be viewed as having four quandrants of N/4 subpixels with the
same color minority subpixels disposed in opposing quadrants, such as shown below,
where P1 is the majority subpixel and P2 and P3 are the two minority primary color
subpixels:
P1 |
P1 |
P2 |
P1 |
P1 |
P3 |
P1 |
P1 |
P3 |
P1 |
P1 |
P2. |
[0089] When a directional display device includes a display panel substantially comprising
one of these subpixel repeating groups, the first (R) and second (L) views are produced
on subpixel repeating groups in which subpixels in one of the primary colors are at
a higher resolution than subpixels of the other two primary colors. These various
subpixel repeating groups illustrated in FIGS. 21B, 21C, 22B, 22C, 23B, 23C, 24B and
24C are previously disclosed and discussed in, or are all variations of subpixel repeating
groups previously disclosed and discussed in
U.S. Patent Application Publication No. 2003/0128225 (
U.S. Application No. 10/278,353), entitled "COLOR FLAT PANEL DISPLAY SUB-PIXEL ARRANGEMENTS AND LAYOUTS FOR SUB-PIXEL
RENDERING WITH INCREASED MODULATION TRANSFER FUNCTION RESPONSE." Thus, when the first
or second view is produced as shown in the figures herein, the image has all of the
advantages and benefits discussed in
US 2003/0128225 with respect to images produced on a display panel substantially comprising the subpixel
arrangements disclosed therein.
[0090] FIG. 21A shows a portion of a display panel 2100 substantially comprising subpixel
repeating group 2110. FIG. 21A shows a portion of display panel 2100 substantially
comprising subpixel repeating group 2110. Subpixel repeating group 2110 comprises
sixteen (16) subpixels disposed in four rows and four columns, and comprising four
red subpixels 2112, eight green subpixels 2114 and four blue subpixels 2116. The green
subpixels 2114 have half the aspect ratio of the red and blue subpixels in the vertical
dimension and are disposed in rows forming horizontal stripes across display panel
2100. If the subpixel repeating group is viewed as having four quadrants of four subpixels
each, then red and blue subpixels are paired in each quadrant, and pairs of red subpixels
2112 and blue subpixels 2116 are disposed in different columns in opposing quadrants,
forming what might be referred to as a double checkerboard pattern. Four subpixels
of three primary colors in a quad grouping, for example the red 2112, two green 2114,
and blue 2116 subpixels, may be viewed as a conventional whole pixel 2120. Thus, display
panel 2100 may be treated as an array of full color conventional whole pixels 2120
when operating in the 2D mode.
[0091] FIG. 21A has columns of subpixels 2124 and 2122 labeled "R" and "L" respectively.
Columns 2124 labeled "R" are directed to a first (R) image and columns 2122 labeled
"L" are directed to a second (L) image when a display device having a display panel
substantially comprising subpixel repeating group 2110 is operated as a directional
display device. FIG. 21B shows view 2104 produced by columns 2124 of subpixels labeled
"R" in FIG. 21A. The image displayed in view 2104 is rendered on a subpixel repeating
group 2130 comprising eight subpixels disposed in four rows, and including four green
subpixels 2114, and two subpixels each of red and blue. Note that the green subpixels
2114 in subpixel repeating group 2130 are disposed in horizontal stripes, and that
green subpixels 2114 form a rectangular arrangement across view 2104. That is, imaginary
lines connecting the centers of four adjacent green subpixels form a rectangle. The
subpixels in subpixel repeating group 2130 occupy substantially the same positions
relative to subpixel repeating group 2110, including the horizontal stripes of green
subpixels 2116 and the checkerboard pattern of the red and blue subpixels. FIG. 21C
shows the view 2102 produced by columns 2122 of subpixels labeled "L" in FIG. 21A.
The image displayed in view 2102 is also rendered on subpixel repeating group 2130.
[0092] With reference to FIG. 21B, an incoming conventional RGB image data set consisting
of right view 2104 may be mapped to the arrangement of subpixels in right view 2104
such that the input green image values are mapped one-to-one with green subpixels
2114 (i.e., one incoming image pixel to one green subpixel) in order to fully reconstruct
the green portion of the input image. The red and blue data values of the input image
data set are reconstructed on the red subpixels 2112 and blue subpixels 2116 that
form respective red and blue resample area arrays, such as described above with respect
to the subpixel rendering operation disclosed in
U.S Patent No. 7,123,277. Several types of filters may be used to accomplish the mapping of the red and blue
color planes. In one method, contributions of the red or blue data values of several
input image pixels are used to produce the data value for a target red or blue subpixel,
according to which input image pixels are used to reconstruct the data values for
the green subpixels that are proximate to the target red or blue subpixel.
[0093] For an example of this type of mapping, refer to FIG. 21B which shows logical pixels
2160 and 2165 each bounded by a dashed-and-dotted line. Overlapping logical pixels
2160 and 2165 are comprised of one each of red, green and blue subpixels for a total
of three subpixels in each logical pixel. In this image mapping example, each logical
pixel 2160 and 2165 contains a unique green subpixel 2114A and 2114B respectively,
and shares its red subpixel and its blue subpixel (e.g., blue subpixel 2116A) with
other adjoining and overlapping logical pixels. Thus, a target blue subpixel 2116A
is surrounded above and below by green subpixels 2114A and 2114B. A box filter is
used to map the blue data values of the two incoming image pixels used to map the
green image data values to adjoining green subpixels 2114A and 2114B. The two values
in the box filter would both be one half (0.5). A similar operation is used for mapping
the input image pixel data to data values for the red subpixels.
[0094] FIG. 22A shows a portion of a display panel substantially comprising subpixel repeating
group 2210. Subpixel repeating group 2210 comprises eight (8) subpixels disposed in
two rows and four columns, and comprising two red subpixels 2212, four green subpixels
2214 and two blue subpixels 2216. The green subpixels 2214 have half the aspect ratio
of the red and blue subpixels in the horizontal dimension and are disposed in two
rows forming vertical stripes down display panel 2200. If the subpixel repeating group
is viewed as having four quadrants of two subpixels each, then red and blue subpixels
are disposed in different columns in opposing quadrants, forming a checkerboard pattern.
Four subpixels of three primary colors in a quad grouping, for example the red 2212,
two green 2214, and blue 2216 subpixels, may be viewed as a conventional whole pixel
2220. Thus, display panel 2200 may be treated as an array of full color conventional
whole pixels 2220 when operating in the 2D mode.
[0095] FIG. 22A has pairs of columns of subpixels 2224 and 2222 labeled "R" and "L" respectively.
Pairs of columns 2224 labeled "R" are directed to a first (R) image and pairs of columns
2222 labeled "L" are directed to a second (L) image when a display device having a
display panel substantially comprising subpixel repeating group 2210 is operated as
a directional display device. FIG. 22B shows view 2204 produced by pairs of columns
2224 of subpixels labeled "R" in FIG. 22A. The image displayed in view 2204 is rendered
on a subpixel repeating group 2230 comprising four subpixels disposed in two rows,
and including two green subpixels 2114, and one subpixel each of red and blue. Note
that the green subpixels 2214 in subpixel repeating group 2230 are also disposed in
vertical stripes; green subpixels 2214 also form a rectangular arrangement across
view 2204. That is, imaginary lines connecting the centers of four green subpixels
form a rectangle. As can be seen from viewing multiple subpixel groups 2230, in view
2204, the red subpixels 2212 are disposed in horizontal stripes alternating with horizontal
stripes of blue subpixels 2216. In contrast to other embodiments disclosed and illustrated
herein, when pairs of columns 2224 of subpixels are directed to the first (R) view
2204, the red and blue subpixels on display panel 2200 of FIG. 22A do not form a checkerboard
pattern across first (R) view 2204. FIG. 22C shows the view 2202 produced by pairs
of columns 2222 of subpixels labelled "L" in FIG. 22A. The image displayed in view
2202 is rendered on subpixel repeating group 2240. Subpixel repeating group 2240 is
similar to subpixel repeating group 2230 with green subpixels 2214 disposed in vertical
stripes, but with the positions of the alternating horizontal stripes of red and blue
subpixels reversed.
[0096] With reference to FIG. 22B, an incoming conventional RGB image data set consisting
of right view 2204 may be mapped to the arrangement of subpixels in right view 22045
such that the input green image values are mapped one-to-one with green subpixels
2214 (i.e., one incoming image pixel to one green subpixel) in order to fully reconstruct
the green portion of the input image. The red and blue data values of the input image
data set are reconstructed on the red subpixels 2212 and blue subpixels 2216 that
form respective red and blue resample area arrays, such as described above with respect
to the subpixel rendering operation disclosed in
U.S. Patent No. 7,123,277. Several types of filters may be used to accomplish the mapping of the red and blue
color planes. In each method, contributions of the red or blue data values of several
input image pixels are used to produce the data value for a target red or blue subpixel,
according to which input image pixels are used to reconstruct the data value for the
green subpixels that are proximate to the target red or blue subpixel.
[0097] For an example of a first type of mapping, refer to FIG. 22B which shows logical
pixel 2260 bounded by a dashed-and-dotted line. Logical pixel 2260 contains four subpixels,
including a unique green subpixel 2214A, and is the logical pixel for target red subpixel
2212A. Three incoming image pixels would be mapped to the data value of target red
subpixel 2212A: a first incoming image pixel that is mapped to the green subpixel
2214A adjacent to target red subpixel 2212A, as well as second and third incoming
image pixels that are mapped to green subpixels 2214B and 2214C positioned above and
below green subpixel 2214A. A tent filter is used to map the red data values of the
first, second and third incoming image pixels to produce a data value for target red
subpixel 2212A. The three values in the tent filter may be one quarter (0.25), one
half (0.5), and one quarter (0.25). A similar operation may be used for mapping the
input image pixel data to data values for the blue subpixels. Consider logical pixel
2262 for target blue subpixel 2216A in FIG. 22B. Using the same tent filter, three
incoming image pixels would be mapped to the data value of target blue subpixel 2216A:
a first incoming image pixel that is mapped to the green subpixel 2214D adjacent to
target blue subpixel 2216A, as well as second and third incoming image pixels that
are mapped to green subpixels 2214E and 2114F positioned above and below green subpixel
2214D. When the subpixel rendering operation is carried out according to this embodiment,
it can be seen that each logical pixel shares a red or blue subpixel with an adjoining
and overlapping logical pixel. Overlapping logical pixels are not explicitly shown
in FIG. 22B to avoid undue complexity in the figure.
[0098] For an example of a second type of mapping, refer to FIG. 22C which shows logical
pixel 2265 bounded by a dashed-and-dotted line. Logical pixel 2260 contains three
subpixels, including a unique green subpixel 2214A, and is the logical pixel for target
blue subpixel 2216A. Two incoming image pixels would be mapped to produce the data
value of target blue subpixel 2216A: a first incoming image pixel that is mapped to
the green subpixel 2214A adjacent to target blue subpixel 2216A, as well as a second
incoming image pixel that is mapped to green subpixel 2214B positioned above green
subpixel 2214A. A box filter is used to map the blue data values of the first and
second incoming image pixels to produce a data value for target blue subpixel 2216A.
The two values in the box filter may both be one half (0.5). A similar operation may
be used for mapping the input image pixel data to data values for the red subpixels.
Using the same box filter, two incoming image pixels would be mapped to produce the
data value of target red subpixel 2212B: a first incoming image pixel that is mapped
to the green subpixel 2214B adjacent to target red subpixel 2212B, as well as a second
incoming image pixel that is mapped to green subpixel 2214A positioned below green
subpixel 2214B. When the subpixel rendering operation is carried out according to
this embodiment, it can be seen that each logical pixel shares a red or blue subpixel
with an adjoining and overlapping logical pixel. Overlapping logical pixels are not
explicitly shown in FIG. 22C to avoid undue complexity in the figure.
[0099] FIG. 23A shows a portion of display panel 2300 substantially comprising subpixel
repeating group 2310. Subpixel repeating group 2310 comprises sixteen (16) subpixels
disposed in four rows and four columns, and comprising four red subpixels 2312, eight
green subpixels 2314, and four blue subpixels 2316. The green subpixels 2314 have
half the aspect ratio of the red and blue subpixels in the vertical dimension and
are disposed within subpixel repeating group 2310 in two rows forming two horizontal
stripes across display panel 2300. If subpixel repeating group 2310 is viewed as having
four quadrants of four subpixels each, then the pairs of red subpixels 2312 and the
pairs of blue subpixels 2316 are disposed in opposing quadrants, forming a double
checkerboard pattern. A group 2320 or quad of four subpixels may be treated as a conventional
"whole" pixel. Thus, the display panel may be treated as an array of full color conventional
whole pixels 2320 when operating in the conventional 2D mode.
[0100] A display device having a display panel substantially comprising subpixel repeating
group 2310 as shown in FIG. 23A may also operate as a directional display device.
FIG. 23B shows the view 2304 produced by columns 2324 of subpixels labeled "R" in
FIG. 23A. The image displayed in view 2304 is rendered on a subpixel repeating group
2330 comprising eight subpixels disposed in four rows and two columns, and including
two red subpixels 2312, two blue subpixels 2316 and four green subpixels 2314 which
form two rows of horizontal stripes. The positions of green subpixels 2314 in view
2304 form a square arrangement across the display panel. That is, imaginary lines
connecting the centers of four adjacent green subpixels form a square. The red subpixels
2312 and the blue subpixels 2316 are diagonally opposed to each other in a checkerboard
pattern.
[0101] FIG. 23C shows the view 2302 produced by columns 2322 of subpixels labeled "L" in
FIG. 23A. The image displayed in view 2302 is also rendered on the same subpixel repeating
group 2330 as produced in view 2304. Thus, the distinct "L" and "R" images produced
on a display panel comprising subpixel repeating group 2310 of FIG. 23A have all of
the advantages discussed therein with respect to images produced on display panels
substantially comprising subpixel arrangement 2330 using a subpixel rendering operation
of the type described therein. In addition, with respect to using subpixel repeating
group 2310 in a directional display system, adjusting the aspect ratios of the green
subpixels 2314 as shown results in keeping the resolution of each of the ordinal axes
in views 2304 and 2302 approximately equal.
[0102] With reference to FIG. 23B, during the subpixel rendering operation that creates
view 2304 (the view labeled "R"), the incoming conventional RGB image data representing
the view 2304 may be mapped to subpixel repeating group 2330 such that the input green
image values are mapped one-to-one with green subpixels 2314 (i.e., one incoming image
pixel to one green subpixel) in order to fully reconstruct the green portion of the
input image. The red and blue data values of the input image data set are reconstructed
on the red subpixels 2112 and blue subpixels 2116 that form respective red and blue
resample area arrays, such as described above with respect to the subpixel rendering
operation disclosed in
U.S Patent No. 7,123,277. Several types of filters may be used to accomplish the mapping of the red and blue
color planes. In general, these filters produce the data value for a target red or
blue subpixel using contributions of the red or blue data values of several input
image pixels that are used to reconstruct the data values for the green subpixels
that are proximate to the target red or blue subpixel.
[0103] For one example of this type of mapping, refer to FIG. 23B which shows one non-contiguous
(NC) logical pixel (hereafter referred to as NC logical pixel) that is bounded by
dashed-and-dotted lines 2360 and 2361. NC logical pixel is the logical pixel for target
blue subpixel 2316A and is comprised of six subpixels. In this image mapping example,
each NC logical pixel contains one unique first primary color subpixel, and one second
primary color subpixel that is the target subpixel for the logical pixel. The first
primary color subpixel is referred to as unique because it is the only green subpixel
included in the logical pixel. In the example shown, NC logical pixel contains a unique
green subpixel 2314A, and one blue subpixel 2316A that is the target subpixel. Each
NC logical pixel further contains four subpixels of the third primary color; in the
example shown, NC logical pixel contains four red subpixels that are not individually
called out in the figure.
[0104] To produce the data value for target blue subpixel 2316A, an area resampling filter
is used that maps the blue data values of five incoming image pixels. A first one
of these five incoming image pixels is the image pixel used to map the green data
value to the unique green subpixel associated with the logical pixel of the target
subpixel. In this example, the logical pixel for target blue subpixel 2316A includes
unique green subpixel 2314A. The input image pixel used to map the green data value
to green subpixel 2314A is the first of the five input image pixels that provide a
contribution to the data value for target blue subpixel 2316A. Second, third, fourth
and fifth input image pixels are identified according to their position relative to
this first input image pixel. Green subpixel 2314A has four nearest green subpixel
neighbors, called out in FIG. 23B as green subpixel 2314B above green subpixel 2314A,
green subpixel 2314C below green subpixel 2314A, and green subpixels 2314D and 2314E
to the right and left respectively of green subpixel 2314A. The blue data value of
each of the input image pixels used to map green data values to these four neighboring
green subpixels provides a contribution to the data value of target blue subpixel
2316A. For convenience, the input image pixel used to map the green data value to
green subpixel 2314A is referred to as the center input image pixel. The area resample
filter that may be used to produce the data value of target blue subpixel 2316A may
contain five values: one eighth (0.125) for each of the four neighboring input image
pixels and one half (0.5) for the center input image pixel. A similar operation may
be used for mapping the input image pixel data to data values for the red subpixels.
[0105] Using this area resampling filter gives rise to overlapping logical pixels, each
of which comprises six subpixels in the configuration of the non-contiguous logical
pixel shown in FIG. 23B having a unique green subpixel, a target red or blue subpixel
and four subpixels of the primary color that is not the target primary color. Overlapping
logical pixels are not explicitly shown in FIG. 23B to avoid undue complexity in the
figure. However, FIG. 23C illustrates a non-contiguous logical pixel that is bounded
by dashed-and-dotted lines 2365 and 2366 for target red subpixel 2312A and having
unique green subpixel 2314F. The same area resampling filter as described above for
producing the data value for a target blue subpixel may be used to produce the data
value for target red subpixel 2312A, using the input image pixel associated with producing
the data value for green subpixel 2314F and the four image input pixels associated
with producing the data values for neighboring green subpixels 2314G, 2314H, 2314J
and 2314K.
[0106] FIG. 24A shows a portion of a display panel 2400 substantially comprising subpixel
repeating group 2410. Subpixel repeating group 2410 comprises twelve (12) subpixels
disposed in two rows and comprising eight green subpixels 2414, two red subpixels
2412 and two blue subpixels 2416. The green subpixels 2414 have half the aspect ratio
of the red and blue subpixels in the horizontal dimension and pairs of narrow green
subpixels form adjacent vertical stripes on display panel 2400. If the subpixel repeating
group is viewed as having four quadrants of three subpixels each, then the red subpixels
2412 and the blue subpixels 2416 are disposed in different rows in opposing quadrants,
forming a low resolution checkerboard pattern.
[0107] FIG. 24A has columns of subpixels 2424, 2422, and 2423 labeled "R," "L" and "B" respectively.
It can be seen from the figure that half of the green subpixel columns are directed
to the first view and half are directed to the second view. Columns 2423 labeled "B"
comprising the red and blue alternating subpixels are directed to both first (R) and
second (L) images when a display device having a display panel substantially comprising
subpixel repeating group 2410 is operated as a directional display device. In this
embodiment, the color primaries are divided into two classes of primaries based on
their relative luminance, and the relatively darker primaries, in this embodiment
the red and blue primary color subpixels, are shared between the left and right views.
As noted above with respect to the other embodiments having columns directed to both
views, this subpixel arrangement exploits a characteristic of the Human Vision System
in which the luminance channel, represented by the subpixels of the brighter primary
colors, has the required resolution to convey the needed stereoscopic information.
The embodiment shown in FIG. 24A, then, is particularly well-suited to autostereoscopic
3D displays and to switchable 2D 3D displays.
[0108] FIG. 24B shows the view 2404 produced by columns 2424 of subpixels labeled "R" and
columns 2423 of subpixels labeled "B" in FIG. 24A. The image displayed in view 2404
is rendered on a subpixel repeating group 2430 comprising eight subpixels disposed
in two rows, and including four green subpixels 2416 disposed in vertical stripes
and two subpixels each of red and blue. The green subpixels 2414 form a square arrangement
across view 2404; that is, imaginary lines connecting the centers of 4 neighboring
green subpixels form a square. The red subpixels 2412 and the blue subpixels 2416
are disposed in opposing quadrants forming a checkerboard pattern. FIG. 24C shows
the view 2402 produced by columns 2422 of subpixels labeled "L" and columns 2423 of
subpixels labeled "B" in FIG. 24A. The image displayed in view 2402 is also rendered
on subpixel repeating group 2430.
[0109] As indicated in the discussion of the other embodiments that have columns of subpixels
that are shared between the left and right views, the subpixel rendering operation
used to render the left and right views may average the contributions for the input
image data belonging to the two separate views 2404 and 2402 for those color planes
corresponding to the color subpixels in the columns 2423 shared by both views. In
the embodiment shown in FIG. 24A, the subpixel rendering operation may average the
contributions for the input image data belonging to the two separate views 2404 and
2402 for the red and blue color planes.
[0110] With reference to FIG. 24C, during the subpixel rendering operation that creates
view 2402 (the view labeled "L"), the incoming conventional RGB image data representing
the view 2402 may be mapped to subpixel repeating group 2430 such that the input green
image values are mapped one-to-one with green subpixels 2414 (i.e., one incoming image
pixel to one green subpixel) in order to fully reconstruct the green portion of the
input image. This is done for the left view 2402 without sharing that data with the
right view 2404 of FIG. 24B. A subpixel rendering operation may be performed on the
input image red and blue data values intended for both the right view 2404 and the
left view 2402 to reconstruct the image data on the red subpixels 2412 and blue subpixels
2416 using respective red and blue resample area arrays, such as described above with
respect to the subpixel rendering operation disclosed in
U.S Patent No. 7,123,277. The results of the subpixel rendering operation may then be averaged. The order
of the subpixel rendering and averaging operations may be interchanged as they are
commutative and distributive mathematical functions. It may prove to be more efficient
(e.g., by reducing the number of digital operations) if the averaging of the two primary
color planes for the right and left views (e.g., the two red input data color planes)
is performed before subpixel rendering.
[0111] Several types of filters may be used to accomplish the subpixel rendering operation
of the red and blue color planes. In general, these filters produce the data value
for a target red or blue subpixel using contributions of the red or blue data values
of several input image pixels that are used to reconstruct the data values for the
green subpixels that are proximate to the target red or blue subpixel. The discussion
of an exemplary subpixel rendering operation for a target blue subpixel 2416A in FIG.
24C that follows below is similar to the discussion of an exemplary subpixel rendering
operation for a target blue subpixel 2316A in FIG. 23B. The reader is referred to
that discussion for any details that may be omitted here.
[0112] FIG. 24C shows one non-contiguous (NC) logical pixel that is bounded by dashed-and-dotted
lines 2470 and 2471. NC logical pixel is the logical pixel for target blue subpixel
2416A and is comprised of six subpixels. In this example, each NC logical pixel contains
one unique first primary color subpixel, and one second primary color subpixel that
is the target subpixel for the logical pixel. The first primary color subpixel is
referred to as unique because it is the only green subpixel in the logical pixel.
In the example shown, NC logical pixel contains a unique green subpixel 2414A, and
one blue subpixel 2416A that is the target subpixel. Each NC logical pixel further
contains four subpixels of the third primary color; in the example shown, NC logical
pixel contains four red subpixels that are not individually called out in the figure.
[0113] To produce the data value for target blue subpixel 2416A, an area resampling filter
is used that maps the blue data values of five incoming image pixels. A first one
of these five incoming image pixels is the image pixel used to map the green data
value to the unique green subpixel associated with the logical pixel of the target
subpixel. In this example, the NC logical pixel for target blue subpixel 2416A includes
unique green subpixel 2414A. The input image pixel used to map the green data value
to green subpixel 2414A is the first of the five input image pixels that provide a
contribution to the data value for target blue subpixel 2416A; this first image pixel
is referred to as the center pixel. Second, third, fourth and fifth input image pixels
are identified according to their position relative to this first input image pixel.
Green subpixel 2414A has four nearest green subpixel neighbors, called out in FIG.
24C as green subpixel 2414B above green subpixel 2414A, green subpixel 2414C below
green subpixel 2414A, green subpixels 2414E to the left of green subpixel 2414A, and
green subpixel 2414D, which, if present on the display panel, is shown to the right
of green subpixel 2414A and red subpixel 2412B. The blue data value of each of the
input image pixels used to map green data values to these four neighboring green subpixels
provides a contribution to the data value of target blue subpixel 2416A. The area
resample filter that may be used to produce the data value of target blue subpixel
2416A may contain five values: one eighth (0.125) for each of the four neighboring
input image pixels and one half (0.5) for the center input image pixel.
[0114] A similar operation may be used for mapping the input image pixel data to data values
for the red subpixels. FIG. 24B shows one non-contiguous logical pixel that is bounded
by dashed-and-dotted lines 2460 and 2461. NC logical pixel is the logical pixel for
target red subpixel 2412A and is comprised of six subpixels, including unique green
subpixel 2414F. To produce the data value for target red subpixel 2412A, an area resampling
filter is used that maps the red data values of the five incoming image pixels that
were used to map green data values to green subpixels 2414F, 2414G, 2414H, 2414J and
2414K. The area resample filter that may be used to produce the data value of target
red subpixel 2412A may be the same area resample filter described above that is used
to produce the data value of target blue subpixel 2416A of FIG. 24C. Note that using
this type of area resampling filter gives rise to overlapping logical pixels. Each
of neighboring green subpixels 2414G, 2414H, 2414J and 2414K is the unique green subpixel
of its own logical pixel. Red subpixels 2412 and blue subpixels 2416 are shared between
views 2404 and 2402 and become part of several overlapping logical pixels. For example,
blue subpixel 2416A of FIG. 24C is the target subpixel of NC logical pixel bounded
by dashed-and-dotted lines 2470 and 2471, and is also contained in NC logical pixel
bounded by dashed-and-dotted lines 2460 and 2461 of FIG. 24B.
[0115] It will be understood by those skilled in the art that various changes may be made
to the exemplary embodiments illustrated herein, and equivalents may be substituted
for elements thereof, without departing from the scope of the appended claims. Therefore,
it is intended that the appended claims include all embodiments falling within their
scope, and not be limited to any particular embodiment disclosed, or to any embodiment
disclosed as the best mode contemplated for carrying out this invention.